High-resilient polyurethane foams produced from polyether polyols

ABSTRACT

Flexible polyurethane foams are produced from a polyisocyanate and a polyether polyol which has been alkoxylated in the presence of a double metal cyanide catalyst and that has at least one ethylene oxide-propylene oxide mixed block.

BACKGROUND OF THE INVENTION

The invention relates to flexible polyurethane foams that have beenproduced from polyisocyanates and polyether polyols in the presence ofdouble metal cyanide (DMC) catalysts and that have at least one ethyleneoxide-propylene oxide mixed block, as well as a process for theirproduction.

The expression flexible polyurethane foams denotes foams that exert asmall resistance to a pressure stress and that are open-cell,air-permeable and that can be reversibly deformed. The properties offlexible polyurethane foams substantially depend on the structure of thepolyether polyols, polyisocyanates and additives such as catalysts andstabilisers that are used in their production. As regards thepolyethers, the functionality, chain length as well as the epoxides usedand the resultant reactivity of the hydroxyl groups have the greatestinfluence on the characteristics of the foam.

The production of polyether polyols is mostly carried out bybase-catalysed polyaddition of alkylene oxides to polyfunctional startercompounds such as for example alcohols, acids, amines, etc. (see forexample Gum, Riese & Ulrich (Editors): “Reaction Polymers”, HanserVerlag, Munich 1992, pp. 75-96). After completion of the polyadditionthe catalyst is removed from the polyether polyol in a very complicatedprocess, for example by neutralisation, distillation and filtration. Thelong-chain polyethers have to be freed particularly carefully fromcatalyst residues since otherwise undesirable secondary reactions suchas for example the formation of polyisocyanurates, may take place duringthe foaming. The residual content of potassium and sodium ions in thepolyether polyol amounts to only a few ppm. Only polyether polyols witha very low alkali metal content are suitable for the production ofpolyurethane elastomers and flexible polyurethane foams. The polyetherpolyols produced by base catalysis also have the disadvantage that withincreasing chain length, the content of monofunctional polyethers(so-called monools) constantly increases and the functionalitydecreases.

In order to circumvent the aforementioned disadvantage, it isrecommended in the field of polyurethane elastomers to employ polyetherpolyols that are produced by using double metal cyanide (DMC) catalysts,and that accordingly have very low contents of allyl ethers (monools)and thus exhibit a higher functionality. Such production processes havebeen known since the 1960s (U.S. Pat. No. 3,427,256, U.S. Pat. No.3,427,334, U.S. Pat. No. 3,427,335). The disadvantage of this productionmethod is however the very complicated and expensive removal of thecatalysts.

In more recent patent applications (for example EP-A 700 949, EP-A 761708, WO 97/40086, WO 98/16310, DE-A 19 745 120, DE-A 19 757 574, DE-A198 102 269) highly active improved DMC catalysts are described, whichon account of their very high activity can be used in such small amounts(catalyst concentration≦50 ppm) that a separation of the catalyst fromthe polyether polyol is no longer necessary. In this way a more economicproduction of the polyether polyols is possible compared to theconventional base-catalysed process. These products may be used directlyfor the production of polyurethane elastomers.

The disadvantage however is that conventional, low molecular weightstarter compounds such as for example propylene glycol, glycerol andtrimethylolpropane cannot in general be alkoxylated with DMC catalysts.The DMC catalysts therefore in general require the use of oligomericpropoxylated starter compounds that are obtained beforehand from theaforementioned low molecular weight starters, for example byconventional alkali catalysis (generally with KOH), followed bycomplicated working-up, by for example neutralisation, distillation andfiltration.

German patent application 198 17 676.7 describes a process for theproduction of long-chain polyether polyols that is completely free ofany working-up stage, in which first of all the pre-propoxylated startercompounds are obtained by catalysis with perfluoroalkyl sulfonates(preferably triflates) of metals of Group III A of the Periodic Systemof the Elements (corresponding to the 1970 IUPAC Convention), which arethen converted without separation of the catalyst and working-up, bymeans of highly active DMC catalysts into long-chain, high molecularweight polyether polyols. An extremely economical production oflong-chain polyether polyols is possible in this way.

The disadvantage however is that poly(oxypropylene)polyols that can beproduced very economically by these highly active DMC catalysts withoutany separation of the DMC catalyst are not suitable for the productionof flexible polyurethane foams. The use of such polyether polyols inflexible foam formulations leads to serious crack formation.

SUMMARY OF THE INVENTION

It has now been found that polyether polyols that are outstandinglysuitable for the production of flexible polyurethane foams are obtainedby the DMC-catalysed incorporation of ethylene oxide/propylene oxidemixed blocks. The mixed blocks are either added directly to thepre-propoxylated starter compounds up to the end of the chain, or areadded only after a propylene oxide block. In both cases a terminalpropylene oxide block can also be added.

Such polyether polyols may also be used without the co-use offiller-containing polyols such as for example polymer polyols(styrene-acrylonitrile copolymers) or polyurea dispersion polyols, etc.,and without modified polyisocyanates such as for example allophanatepolyisocyanates, biuret polyisocyanates, for the production of flexiblepolyurethane foams. Traces of catalyst do not in this case exert anynegative influence.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the apparatus used to determine the air permeabilityof the foam produced in Example 12.

FIG. 2 illustrates in detail the glass flow vessel of the apparatusshown in FIG. 1.

FIG. 3 illustrates in detail the measuring head of the apparatus shownin FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The invention accordingly provides flexible polyurethane foams ofpolyisocyanates and long-chain polyether polyols that are produced byDMC catalysis without separation of the catalyst, that have at least oneethylene oxide/propylene oxide mixed block, and that also have a numberaverage molecular weight between 700 and 15,000 g/mole, as well as aprocess for their production.

Suitable as polyisocyanates are aliphatic, cycloaliphatic, araliphatic,aromatic and heterocyclic polyisocyanates, such as are described inJustus Liebigs Annalen der Chemie 562 (1949) 75, for example those ofthe formulaQ(NCO)_(n)in which

-   -   n is an integer from 2 to 4, preferably 2, and    -   Q denotes an aliphatic hydrocarbon radical with 2 to 18,        preferably 6 to 10 C atoms, a cycloaliphatic hydrocarbon radical        with 4 to 15, preferably 5 to 10 C atoms, an aromatic        hydrocarbon radical with 6 to 15, preferably 6 to 13 C atoms, or        an araliphatic hydrocarbon radical with 8 to 15, preferably 8 to        13 C atoms.

Preferred are polyisocyanates such as are described in DE-OS 2 832 253.As a rule it is particularly preferred to use the technically easilyaccessible polyisocyanates, for example 2,4-toluylene diisocyanate and2,6-toluylene diisocyanate as well as arbitrary mixtures of theseisomers (“TDI”), polyphenyl-polymethylene polyisocyanates, such as areproduced by aniline-formaldehyde condensation followed by phosgenation(“crude MDI”) and polyisocyanates containing carbodiimide groups,urethane groups, allophanate groups, isocyanurate groups, urea groups orbiuret groups (“modified polyisocyanates”), in particular those modifiedpolyisocyanates that are derived from 2,4-toluylene diisocyanate and/or2,6-toluylene diisocyanate or from 4,4′-diphenylmethane diisocyanateand/or 2,4′-diphenylmethane diisocyanate.

The production of the long-chain polyether polyols that are used in theprocess according to the invention is carried out by means ofDMC-catalysed polyaddition of alkylene oxides to starter compoundscontaining active hydrogen atoms.

Suitable DMC catalysts are in principle known and are described indetail in the prior art listed above. There are preferably usedimproved, highly active DMC catalysts that are described for example inEP-A 700 949, EP-A 761 708, WO 97/40086, WO 98/16310, DE-A 197 45 120,DE-A 197 57 574 and DE-A 198 102 269. A typical example are the highlyactive DMC catalysts described in EP-A 700 949 that contain, in additionto a double metal cyanide compound (for example zinchexacyanocobaltate(III)) and an organic complex ligand (for exampletert.-butanol), also a polyether with a number average molecular weightof greater than 500 g/mole.

As starter compounds with active hydrogen atoms there are preferablyused compounds with (number average) molecular weights of 18 to 2,000g/mole and with 1 to 8 hydroxyl groups. By way of example there may bementioned butanol, ethylene glycol, diethylene glycol, triethyleneglycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, bisphenolA, trimethylolpropane, glycerol, pentaerythritol, sorbitol, cane sugar,degraded starch or water.

It is more advantageous to use those starter compounds with activehydrogen, atoms that have been produced beforehand from theaforementioned low molecular weight starter compounds and that formoligomeric alkoxylation products with (number average) molecular weightsof 200 to 2,000 g/mole. Preferably oligomeric propoxylated startercompounds are used having 1 to 8 hydroxyl groups, particularlypreferably 2 to 6 hydroxyl groups, and (number average) molecularweights of 200 to 2,000 g/mole.

The production of these oligomeric propoxylated starter compounds fromthe low molecular weight starters may be carried out for example byconventional alkali catalysis (e.g. with KOH) followed by working-up byfor example neutralisation, distillation and filtration, or as describedin German patent application 198 17 676.7 by catalysis withperfluoroalkyl sulfonates of metals of Group III A of the PeriodicSystem of the Elements (corresponding to the 1970 IUPAC Convention),without subsequent separation of the catalyst.

The further alkoxylation is then carried out with highly active DMCcatalysts. According to the invention the pre-propoxylated startercompound is converted by means of DMC catalysis either with an EO/POmixed block in a weight ratio of 2/98 to 90/10, or is furtherpropoxylated and then reacted either with an EO/PO mixed block in aweight ratio of 2/98 to 90/10, or is first of all reacted with an EO/POmixed block in a weight ratio of 2/98 to 90/10 and at the end is reactedonce more with a PO block, or is further propoxylated and then reactedwith an EO/PO mixed block in a weight ratio of 2/98 to 90/10 and at theend is reacted once more with a PO block.

The DMC-catalysed alkoxylation is generally carried out at temperaturesof 20 to 200° C., preferably in the range from 40 to 180° C.,particularly preferably at temperatures of 50 to 150° C. The reactionmay be carried out at total pressures of 0.001 to 20 bar. Thepolyadditon may be carried out in bulk or in an inert, organic solventsuch as toluene and/or THF. The amount of solvent is normally 10 to 30wt. % referred to the amount of the polyether polyol to be produced. Thepolyaddition may be carried out continuously or batchwise, for examplein a batch or in a semi-batch process.

The weight ratios of the EO/PO mixed blocks to be reacted is 2/98 to90/10, preferably 5/95 to 80/20. The length of the EO/PO mixed blocks aswell as of the pure PO blocks that are built up by means of DMCcatalysis is in each case 1 to 1,000 alkylene oxide units, preferably 2to 500 alkylene oxide units, and particularly preferably 3 to 200alkylene oxide units.

If the polyether polyols produced by DMC catalysis have a terminal EO/POmixed block, then these are preferably produced with an ethyleneoxide/propylene oxide mixture in an EO:PO weight ratio of 40:60 to 95:5,preferably 50:50 to 90:10, particularly preferably 60:40 to 90:10. Insuch polyether polyols the proportion of primary OH groups is preferably40 to 95 mole %, particularly preferably 50 to 90 mole %; the totalcontent of oxyethylene units in the polyether polyol is preferably >25wt. %, particularly preferably>30 wt. %, most particularly preferably>35wt. %.

The number average molecular weights of the long-chain polyether polyolsthat are used according to the invention for the production of flexiblepolyurethane foams are 700 to 50,000 g/mole, preferably 1,000 to 30,000g/mole, and particularly preferably 1,500 to 20,000 g/mole.

The concentration of the highly active DMC catalysts is 5 to 100 ppm,preferably 10 to 75 ppm and particularly preferably 15 to 50 ppm,referred to the amount of the polyether polyol to be produced. Onaccount of the very low catalyst concentration the polyether polyols maybe used without separation of the catalyst for the production offlexible polyurethane foams without the product qualities beingadversely affected.

In addition to the aforedescribed long-chain polyether polyols producedby DMC catalysis without separation of the catalyst, further compoundscontaining hydroxyl groups (polyols) may be used in the polyolformulation for the production of the flexible polyurethane foamsaccording to the invention. These polyols known per se are described indetail for example in Gum, Riese & Ulrich (Editors): “reactionPolymers”, Hanser Verlag, Munich 1992, pp. 66-96, and G. Oertel(Editor): “Kunststoffhandbuch, Vol. 7, Polyurethanes”, Hanser Verlag,Munich 1993, pp. 57-75. Examples of suitable polyols may be found in theaforementioned literature citations as well as in U.S. Pat. No.3,652,639, U.S. Pat. No. 4,421,872 and U.S. Pat. No. 4,310,632.

Preferably used polyols are polyether polyols (in particularpoly(oxyalkylene)polyols) and polyester polyols.

The production of the polyether polyols is carried out according toknown methods, preferably by base-catalysed polyaddition of alkyleneoxides to polyfunctional starter compounds containing active hydrogenatoms, such as for example alcohols or amines. The following may bementioned by way of example: ethylene glycol, diethylene glycol,1,2-propylene glycol, 1,4-butanediol, hexamethylene glycol, bisphenol A,trimethylolpropane, glycerol, pentaerythritol, sorbitol, cane sugar,degraded starch, water, methylamine, ethylamine, propylamine,butylamine, aniline, benzylamine, o- and p-toluidine, α,β-naphthylamine, ammonia, ethylenediamine, propylenediamine,1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5-, and/or1,6-hexamethylendiamine, o-, m-, and p-phenylenediamine, 2,4-,2,6-toluylenediamine, 2,2′-, 2,4- and 4,4′-diaminodiphenylmethane anddiethylenediamine.

As alkylene oxides there are preferably used ethylene oxide, propyleneoxide, butylene oxide as well as their mixtures. The build-up of thepolyether chains by alkoxylation may be carried out not only with onemonomeric epoxide, but also statistically or also blockwise with two orthree different monomeric epoxides.

Processes for the production of such polyether polyols are described in“Kunststoffhandbuch, Vol. 7, Polyurethanes”, in “Reaction Polymers” aswell as for example in U.S. Pat. No. 1,922,451, U.S. Pat. No. 2,674,619,U.S. Pat. No. 1,922,459, U.S. Pat. No. 3,190,927 and U.S. Pat. No.3,346,557.

Methods for the production of polyester polyols are also well known andare described for example in the two aforementioned literature citations(“Kunststoffhandbuch, Vol. 7, Polyurethanes”, and “Reaction Polymers”).The polyester polyols are produced inter alia by polycondensation ofpolyfunctional carboxylic acids or their derivatives, such as forexample acid chlorides or anhydrides, with polyfunctional hydroxylcompounds.

As polyfunctional carboxylic acids there may for example be used: adipicacid, phthalic acid, isophthalic acid, terephthalic acid, oxalic acid,succinic acid, glutaric acid, azelaic acid, sebacic acid, fumaric acidor maleic acid.

As polyfunctional hydroxyl compounds there may for example be used:ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propyleneglycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol,1,6-hexanediol, 1,12-dodecanediol, neopentyl glycol, trimethylolpropane,triethylolpropane or glycerol.

The production of the polyester polyols may furthermore also be carriedout by ring-opening polymerisation of lactones (e.g. caprolactone) withdiols and/or triols as starters.

In addition a crosslinking component may be added in the production ofthe flexible polyurethane foams according to the invention. Crosslinkingcomponents that may be used are for example diethanolamine,triethanolamine, glycerol, trimethylolpropane (TMP), adducts of suchcrosslinking compounds with ethylene oxide and/or propylene oxide withan OH number<1,000, or also glycols with a number average molecularweight of ≦1,000. Particularly preferred are triethanolamine, glycerol,TMP or low molecular weight EO and/or PO adducts thereof.

In addition auxiliary substances and additives and/or flame retardantsknown per se may also optionally be added as further components. In thisconnection auxiliary substances are understood to mean in particularcatalysts and stabilisers known per se. Melamine may for example be usedas flame retardant.

Catalysts that may optionally be added are known per se. By way ofexample there may be mentioned tertiary amines such as triethylamine,tributylamine, N-methylmorpholine, N-ethylmorpholine,N,N,N′,N′-tetramethylethylenediamine, pentamethyldiethylenetriamine andhigher homologues (DE-A 26 24 527 and DE-A 26 24 528),1,4-diaza-bicyclo[2,2,2]octane,N-methyl-N′-dimethylaminoethyl-piperazine,bis(dimethylaminoalkyl)piperazines (DE-A 26 36 787),N,N-dimethylbenzylamine, N,N-dimethylcyclohexylamine,N,N-diethylbenzylamine, bis(N,N-diethylaminoethyl)adipate,N,N,N′,N′-tetramethyl-1,3-butanediamine,N,N-dimethyl-β-phenylethylamine, 1,2-dimethylimidazole,2-methylimidazole, monocyclic and bicyclic amidines (DE-A 17 20 633),bis(dialkylamino)alkyl ethers (U.S. Pat. No. 3,330,782, DE-A 10 30 558,DE-A 18 04 361 and DE-A 26 18 280) as well as tertiary amines containingamide groups (preferably formamide groups) according to DE-A 25 23 633and DE-A 27 32 292. Also suitable as catalysts are Mannich bases knownper se formed from secondary amines, for example dimethylamine, andaldehydes, preferably formaldehyde, or ketones such as acetone, methylethyl ketone or cyclohexanone, and phenols such as phenol, nonyl phenolor bisphenols. Tertiary amines having hydrogen atoms active with respectto isocyanate groups and that may be used as catalyst are for exampletriethanolamine, triisopropanolamine, N-methyldiethanol amine,N-ethyldiethanolamine. N,N-dimethylethanolamine, their reaction productswith alkylene oxides such as propylene oxide and/or ethylene oxide, aswell as secondary-tertiary amines according to DE-A 27 32 292. Alsosuitable as catalysts are silaamines with carbon-silicon bonds, such asare described for example in DE-A 12 29 290, for example2,2,4-triethyl-2-silamorpholine and1,3-diethylaminomethyltetramethyldisiloxane. There may also be used ascatalysts nitrogen-containing bases such as tetaalkylammoniumhydroxides, as well as alkali metal hydroxides such as sodium hydroxide,alkali metal phenolates such as sodium phenolate, or alkali metalalcoholates such as sodium methylate. Hexahydrotriazines may also beused as catalyst (DE-A 17 69 043). The reaction between NCO groups andZerewitinoff-active hydrogen atoms is also greatly accelerated bylactams and azalactams, an associate between the lactam and the compoundcontaining acidic hydrogen first of all being formed. Such associatesand their catalytic action are described in DE-A 20 62 286, DE-A 20 62289, DE-A 21 17 576, DE-A 21 29 198, DE-A 23 30 175 and DE-A 23 30 211.According to the invention organometallic compounds, in particularorganic tin compounds, may also be used as catalysts. As organic tincompounds there may be used, in addition to sulfur-containing compoundssuch as di-n-octyltin mercaptide (DE-A 17 69 367; U.S. Pat. No.3,645,927), preferably tin(II) salts of carboxylic acids such astin(II)acetate, tin(II)octoate, tin(II)ethylhexanoate andtin(II)laurate, and tin(W) compounds, for example dibutyltin oxide,dibutyltin dichloride, dibutyltin diacetate, dibutyltin dilaurate,dibutyltin maleate or dioctyltin diacetate. Obviously all of theaforementioned catalysts may be used in the form of mixtures. Ofparticular interest in this connection are combinations oforganometallic compounds and amidines, aminopyridines orhydrazinopyridines (DE-A 24 34 185, DE-A 26 01 082 and DE-A 26 03 834).So-called polymeric catalysts such as are described in DE-A 42 18 840may furthermore be used as catalysts. These catalysts are reactionproducts, present in the form of alkali metal salts, of trifunctional orhigher functional alcohols with (number average) molecular weights of 92to 1,000 with intramolar carboxylic acid anhydrides. The reactionproducts have (statistical average) at least 2, preferably 2 to 5hydroxyl groups, and at least 0.5, preferably 1.0 to 4 carboxylategroups, the counterions to the carboxylate groups being alkali cations.The “reaction products” of the starting components may, as is evidentfrom the content of carboxylate groups, also be mixtures of truereaction products with excess amounts of alcohols. Suitable polyhydricalcohols for the production of the reaction products are for exampleglycerol, trimethylolpropane, sorbitol, pentaerythritol, mixtures ofsuch polyhydric alcohols, alkoxylation products of alcohols with (numberaverage) molecular weights of 92 to 1,000 of such polyhydric alcohols orof mixtures of such alcohols, wherein in the alkoxylation propyleneoxide and/or ethylene oxide may be used in arbitrary sequence or as amixture, though preferably exclusively propylene oxide is used. Suitableintramolecular carboxylic acid anhydrides for the production of thereaction product are for example maleic anhydride, phthalic anhydride,hexahydrophthalic anhydride, succinic anhydride, pyromellitic anhydrideor arbitrary mixtures of such anhydrides. It is particularly preferredto use maleic anhydride. Further examples of catalysts that may be usedas well as details of the mode of action of the catalysts are describedin Vieweg und Höchtlen (Editors): Kunststoff-Handbuch, Vol. VII,Carl-Hanser-Verlag, Munich 1966, pp. 96-102.

The catalysts are as a rule used in amounts of about 0.001 to 10 wt. %,referred to the total amount of compounds having at least two hydrogenatoms reactive with respect to isocyanates.

Further additives that may optionally be used are surface-activeadditives such as emulsifiers and foam stabilisers. Suitable emulsifiersare for example the sodium salts of castor oil sulfonates or salts offatty acids with amines such as oleic acid diethylamine or stearic aciddiethanolamine. Alkali metal salts or ammonium salts of sulfonic acids,such as for example of dodecylbenzenesulfonic acid ordinaphthylmethanedisulfonic acid or of fatty acids such as castor oilacid or of polymeric fatty acids may also be co-used as surface-activeadditives.

As foam stabilisers there may be used in particular polyether siloxanes,especially water-soluble examples. These compounds are generallysynthesised in such a way that a copolymer of ethylene oxide andpropylene oxide is joined to a polydimethylsiloxane radical. Such foamstabilisers are described for example in U.S. Pat. No. 2,834,748, U.S.Pat. No. 2,917,480 and U.S. Pat. No. 3,629,308. Of particular interestare polysiloxane-polyoxyalkylene copolymers multiply branched viaallophanate groups, according to DE-A 25 58 523.

Further possible additives are reaction retardants, for exampleacid-reacting substances such as hydrochloric acid or organic acidhalides, also cell regulators known per se such as paraffins or fattyalcohols or dimethylpolysiloxanes, as well as pigments, dyes and flameretardants known per se, for example trichloroethyl phosphate, tricresylphosphate or ammonium phosphate and ammonium polyphosphate, furthermorestabilisers against the effects of ageing and weathering, plasticisers,and fungistatic and bacteriostatic acting substances, and also fillerssuch as barium sulfate, diatomaceous earth, carbon black or precipitatedchalk.

Further examples of surface-active additives and foam stabilisers thatmay optionally be co-used according to the invention, as well as cellregulators, reaction retardants, stabilisers, flame-inhibitingsubstances, plasticisers, dyes and fillers and also fungistatic andbacteriostatic acting substances, as well as details of the use and modeof action of these additives are described in Vieweg und Höchtlen(Editors): Kunststoff-Handbuch, Vol. VII, Carl-Hanser-Verlag, Munich1966, pp. 103-113.

Blowing agent components that may optionally be used are all knownblowing agents in polyurethane foam production. Suitable organic blowingagents include for example acetone, ethyl acetate, halogen-substitutedalkanes such as methylene chloride, chloroform, ethylidene chloride,vinylidene chloride, monofluorotrichloromethane, chlorodifluoromethane,dichlorodifluoromethane, and also butane, hexane, heptane ordiethylether, while suitable inorganic blowing agents are for exampleair, CO₂ or N₂O. A blowing action can also be achieved by addingcompounds that decompose at temperatures above room temperature with therelease of gases, for example nitrogen, examples of such compounds beingazo compounds such as azo dicarbonamide or azo isobutyronitrile.Particularly preferred as blowing agents are hydrogen-containingfluoroalkanes (HCFCs) as well as lower alkanes such as for examplebutane, pentane, isopentane, cyclopentane, hexane, isohexane, optionallymixed with one another and/or with the addition of water. Furtherexamples of blowing agents as well as details of their use are describedin Vieweg und Höchtlen (Editors): Kunststoff-Handbuch, Vol. VII,Carl-Hanser Verlag, Munich 1966, pp. 108 et seq., pp. 453 et seq., andpp. 507 et seq. However, it is preferred to use water or CO₂ as the soleblowing agent.

In order to carry out the process according to the invention thereaction components are reacted according to the one-stage process knownper se, the prepolymer process or the semi-prepolymer process, whereinmechanical equipment such as described in U.S. Pat. No. 2,764,565 ispreferably used. Details of processing equipment that may also be usedaccording to the invention are given in Vieweg und Höchtlen (Editors):Kunststoff-Handbuch, Vol. VII, Carl-Hanser-Verlag, Munich 1966, pp. 121to 205.

In the production of the foam the foaming may also be carried outaccording to the invention in closed moulds. For this, the reactionmixture is added to a mould, suitable mould materials being metals, forexample aluminium, or plastics materials, for example epoxide resin. Thefoamable reaction mixture foams in the mould and forms the mouldedarticle. The mould foaming may be carried out in such a way that thesurface of the moulded part has a cellular structure. The foaming mayhowever also be carried out so that the moulded part has a complete skinand a cellular core. According to the invention, in this connection thefoaming may be carried out in such a way that sufficient foamablereaction mixture is added to the mould so that the foam that is formedjust fills the mould. Alternatively however, more foamable reactionmixture may be added to the mould than is necessary to fill the interiorof the mould with foam. In the latter case the process is carried outunder so-called “overcharging” conditions; such a procedure is known forexample from U.S. Pat. No. 3,178,490 and U.S. Pat. No. 3,182,104.

In the mould foaming process, in many cases “external release agents”known per se, such as silicone oils, are co-used. However, so-called“internal release agents” may also be used, optionally mixed withexternal release agents, as is disclosed for example in DE-OS 21 21 670and DE-OS 23 07 589.

Obviously, foamed materials may however also be produced by blockfoaming or by the double conveyor belt process known per se (see“Kunststoffhandbuch”, Vol. VII, Carl Hanser Verlag, Munich, Vienna,3^(rd) Edition 1993, p. 148).

The foamed materials may be produced by various processes used in theproduction of block foams, but also in moulds. In the production ofblock foams, in a preferred embodiment of the invention polyetherpolyols are used that contain EO/PO mixed blocks with a PO proportion ofat least 50 mole %, preferably at least 60 mole %; in addition they mayalso contain terminal PO blocks. If very flexible foams are to beproduced, then polyether polyols are used that contain EO/PO mixedblocks with a large proportion of oxyethylene units; preferably thesepolyols also have a large proportion of primary OH groups (preferably atleast 40 mole %, particularly preferably at least 50 mole %). In thisconnection these polyether polyols may be used in combination withconventionally produced polyols containing a large proportion of primaryOH groups. In order to produce hot-cured moulded foams polyether polyolsare preferably used containing at least one internal EO/PO mixed blockand terminal PO block, while for the production of cold-cured mouldedfoams polyether polyols with a terminal EO/PO mixed block and aproportion of primary OH groups of more than 40 mole %, in particularmore than 50 mole %, have proved particularly suitable.

EXAMPLES

Production of the DMC Catalyst (According to EP-A 700 949).

A solution of 12.5 g (91.5 mmole) of zinc chloride in 20 ml of distilledwater is added while stirring vigorously (24,000 revs/min) to a solutionof 4 g (12 mmole) of potassium hexacyanocobaltate in 70 ml of distilledwater. Immediately thereafter a mixture of 50 g of tert.-butanol and 50g of distilled water is added to the resultant suspension and the wholeis then vigorously stirred for 10 minutes (24,000 revs/min). A mixtureof 1 g of polypropylene glycol with a mean molecular weight of 2,000, 1g of tert.-butanol and 100 g of distilled water is then added andstirred for 3 minutes (1,000 revs/min). The solids are removed byfiltration, then stirred for 10 minutes (10,000 revs/min) with a mixtureof 70 g of tert.-butanol, 30 g of distilled water and 1 g of the abovepolyether, and refiltered. Finally, the product is stirred once more(10,000 revs/min) for 10 minutes with a mixture of 100 g oftert.-butanol and 0.5 g of the above polyether. After filtration thecatalyst is dried to constant weight at 50° C. and under normalpressure.

Yield of dried, pulverulent catalyst: 6.23 g

Elementary analysis and thermogravimetric analysis:

Cobalt=11.6 wt. %, zinc=24.6 wt. %, tert.-butanol=3.0 wt. %,polyether=25.8 wt. %

Production of Polyether Polyols

Example 1

746.7 g of a poly(oxypropylene)triol starter compound (hydroxylnumber=431 mg KOH/g) that had been produced from glycerol and propyleneoxide by yttrium triflate catalysis (100 ppm) without separation of thecatalyst, and 0.6 g of DMC catalyst (100 ppm, referred to the amount ofthe long-chain polyol to be produced) are placed under a protective gas(nitrogen) in a 10 L capacity glass pressure flask and heated to 105° C.while stirring. Propylene oxide (ca. 100 g) is then added in one gountil the total pressure has risen to 1.5 bar. Further propylene oxideis then added only when an accelerated drop in pressure is observed.This accelerated drop in pressure indicates that the catalyst isactivated. The residual propylene oxide (3,408.4 g) is then continuouslymetered in at a constant overall pressure of 1.5 bar. After adding allthe propylene oxide and a post-reaction time of 5 hours at 105° C.,581.6 g of ethylene oxide and 1,163.2 g of propylene oxide are added ina mixed block at temperatures of 100-110° C. After a post-reaction timeof 5 hours volatile fractions are distilled off at 105° C. (1 mbar),following which the contents are cooled to room temperature and 6 g ofan antioxidant (3,5-ditert.-butyl-4-hydroxytoluene, BHT) are added.

The long-chain polyether polyol obtained has an OH number of 54.7 mgKOH/g and a double bond content of 7 mmole/kg.

Example 2

As Example 1, but instead using 1,182.0 g of propylene oxide, a mixedblock of 581.6 g of ethylene oxide and 2,326.5 g of propylene oxide, anda terminal block of 1,163.2 g of propylene oxide.

The product has an OH number of 54.4 mg KOH/g and a double bond contentof 8 mmole/kg.

Example 3

872.7 g of a poly(oxypropylene)triol starter compound (hydroxylnumber=380 mg KOH/g) that has been produced by KOH catalysis from TMPand propylene oxide, and 0.3 g of DMC catalyst (50 ppm, referred to theamount of the long-chain polyol to be produced) are added under aprotective gas (nitrogen) to a 10 L capacity glass pressure flask andheated to 105° C. while stirring. A mixture of propylene oxide (541.3 g)and ethylene oxide (4,586.0 g) is then continuously added at a constantoverall pressure of 1.5 bar. After a post-reaction time of 5 hoursvolatile fractions are distilled off at 105° C. (1 mbar), followingwhich the contents are cooled to room temperature and 6 g of anantioxidant (3,5-ditert.-butyl-4-hydroxytoluene, BHT) are added.

The long-chain polyether polyol obtained has an OH number of 58.5 mgKOH/g and a double bond content of 2 mmole/kg.

Example 4

As Example 3, but with a mixed block consisting of 4,614.6 g ofpropylene oxide and 512.7 g of ethylene oxide.

The long-chain polyether polyol obtained has an OH number of 58.1 mgKOH/g and a double bond content of 7 mmole/kg.

Example 5

As Example 3, but with a mixed block consisting of 3,589.1 g of ethyleneoxide and 1,538.2 g of propylene oxide.

The product has an OH number of 59.1 mg KOH/g and a double bond contentof 2 mmole/kg.

Example 6

As Example 3, but with a mixed block consisting of 1,719.8 g of ethyleneoxide and 3,407.4 g of propylene oxide.

The product has an OH number of 58.5 mg KOH/g and a double bond contentof 4 mmole/kg.

Comparison Example 1

746.7 g of a poly(oxypropylene)triol starter compound (hydroxylnumber=431 mg KOH/g) that has been produced from glycerol and propyleneoxide by yttrium triflate catalysis (100 ppm) without separation of thecatalyst, and 0.6 g of DMC catalyst (100 ppm, referred to the amount ofthe long-chain polyol to be produced) are placed under a protective gas(nitrogen) in a 10 L capacity glass pressure flask and heated to 105° C.while stirring. Propylene oxide (ca. 100 g) is then added in one gountil the overall pressure has risen to 1.5 bar. Further propylene oxideis then added only when an accelerated drop in pressure is observed.This accelerated drop in pressure indicates that the catalyst isactivated. The residual propylene oxide (5,153.3 g) is then continuouslyadded at a constant overall pressure of 1.5 bar. After adding all thepropylene oxide and a post-reaction time of 5 hours at 105° C., volatilefractions are distilled off at 105° C. (1 mbar), and the contents arethen cooled to room temperature.

The long-chain polyether polyol obtained has an OH number of 54.4 mgKOH/g and a double bond content of 10 mmole/kg.

Production of Flexible Polyurethane Foams

Production of the Flexible Foams:

Free Foam

a) Cold-Cured Moulded Foam

The polyol formulation is weighed out according to the formulationinstructions on high-speed laboratory scales. In this connection thecorresponding polyether (optionally polyether mixture) is added to theconventional laboratory cardboard beaker provided for this purpose andheated to 25° C. After briefly swirling the contents all the necessaryadditives according to the formulation details are added. After thepolyether formulation has been heated to 25° C., the sample is stirredfor 30 seconds using an LM-34 stirrer at maximum speed (4,200 revs/min)in order to produce a homogeneous mixture and to ensure a uniformcharging with air. In this connection care should be taken to ensurethat the stirrer tray does not touch the sheet metal floor of thevessel.

The isocyanate/isocyanate mixture heated to 25° C. is weighed outaccording to the quantitative instructions on high-speed laboratoryscales and added to a suitable beaker. The thus previously preparedquantity of isocyanate is added to the reaction vessel together with thepolyether formulation. In this connection care should be taken to ensurethat the outflow time of the isocyanate component is about 3 seconds.The components are then stirred in the reaction vessel by means of anLM-34 stirrer at 4,200 revs/min. When the mixture has assumed a creamyconsistency (starts to rise), part of the reaction mixture isimmediately transferred to a small paper packet stabilised by means of awooden box.

Starting time is the period from the beginning of the mixing stage up tothe clearly recognisable start of the reaction.

The setting time (“thread drawing time”) is a measure of the polymerformation reaction, and is determined by repeatedly inserting a thinround wooden rod into the rising reaction mixture shortly before theexpected setting time (empirical value).

The time period from the start of mixing up to the time at which threads(TDI or TDI/MDI systems) or pocks (MDI systems) form or remain hangingwhen the round wooden rod is withdrawn, is taken as the setting time.

The rise time is understood to be the time period between the start ofmixing and the maximum vertical foam height.

b) Hot-Cured Foam

Polyether, water, activator and stabiliser are mixed for 30 seconds(LM-34 stirrer, 4,200 revs/min), following which the crosslinking agent(tin octoate SO) is weighed out and mixed with the reaction mixture. Thecalculated quantity of isocyanate is then added to the reaction vesseltogether with the polyether formulation. In this connection care shouldbe taken to ensure that the outflow time of the isocyanate component isabout 3 secs. The components are then stirred in the reaction vesselwith an LM-34 stirrer at 4,200 revs/min.

When the mixture has assumed a creamy consistency (starts to rise), partof the reaction mixture is immediately transferred to a small paperpacket stabilised by means of a wooden box.

Starting time is the period from the beginning of the mixing stage up tothe clearly recognisable start of the reaction.

Rise time: the term rise time is understood to mean the interval betweenthe start of mixing and the maximum vertical foam height. With hot-curedfoams a deflation is also observed.

30 seconds after the end of the rise time the small packet is placed ina cabinet heated at 150° C. Residence time 5 min.

Moulded Part (Cold-Cured Moulded Foam)

The reaction mixture is transferred to a mould (mould temperature 50-60°C.) that is provided with a commercially available release agent. Themould is closed with a cover and transferred to a press or closeablecontainer in order to counteract the foam pressure and to keep the toolclosed. After 5 minutes the cover is removed and the foam is processedby mechanical crushing (for example by hand, with punches or rollers orby pressure reduction) until the foam has an open-cell structure(shrinkage-free).

Moulded Part (Hot-Cured Moulded Foam)

The reaction mixture is transferred to a mould (mould temperature 40-45°C.) and the mould is closed with a perforated cover.

30 seconds after the end of the rise time (deflation) the mould isplaced in the heated cabinet at 150° C. Residence time 15 min.

After removal from the heated cabinet the hot mould is sprayed withrelease agent (Acmos® 32-574, Acmos Chemie GmbH & Co., D-28199 Bremen).

Comparison Example 2

100 parts by weight of the polyether from Comparison Example 1 3.0 partsby weight water 0.5 parts by weight silicone stabiliser (OS ® 15, Th.Goldschmidt AG, D-45127 Essen) 0.1 parts by weightN,N′-dimethylethanolamine (DMEA) 0.05 parts by weight amine catalyst(Niax ® A1, Witco Osi) 0.34 parts by weight tin octoate 35.6 parts byweight toluylene diisocyanate (65 wt. % 2,4-isomer, 35 wt. % 2,6-isomer;Desmodur ® T 65, Bayer AG)were thoroughly mixed and foamed to form a foam. The block exhibited ahorizontal internal crack that could not be rectified either by varyingthe tin catalyst (0.24-0.38 part by weight) or by the NCO/OH ratio(characteristic number 102-108).

Example 7

100 parts by weight of the polyether from Example 4 4.0 parts by weightwater 0.4 parts by weight silicone stabiliser (OS ® 25, Th. GoldschmidtAG, D-45127 Essen) 0.1 parts by weight DMEA 0.05 parts by weight aminecatalyst (Niax ® A1, Witco Osi) 0.18 parts by weight tin octoate 51.2parts by weight toluylene diisocyanate (80 wt. % 2,4-isomer, 20 wt. %2,6-isomer; Desmodur ® T 80, Bayer AG)were thoroughly mixed and foamed to form a foam block. A crack-free,open foam with a regular cell structure was obtained.

Example 8

100 parts by weight of the polyether from Example 6 4.0 parts by weightwater 0.4 parts by weight silicone stabiliser (OS ® 25, Th. GoldschmidtAG, D-45127 Essen) 0.1 parts by weight DMEA 0.05 parts by weight aminecatalyst (Niax ® A1, Witco Osi) 0.18 parts by weight tin octoate 51.2parts by weight Desmodur ® T 65were thoroughly mixed and foamed to form a foam block. A crack-free foamhaving a regular cell structure was obtained.

Example 9

In a formulation for producing super-flexible qualities, the polyetherfrom Example 5 was foamed as a mixture with an active conventionalpolyether:

75 parts by weight of the polyether from Example 5 25 parts by weight ofa trifunctional polyether with an OH number of 35 mg KOH/g and primaryOH groups > 80 mole % (Desmophen ® 3900 I, Bayer AG) 3.50 parts byweight water 0.8 parts by weight silicone stabiliser (OS ® 15, Th.Goldschmidt AG, D45127 Essen) 0.7 parts by weight DMEA 0.25 part byweight amine catalyst (catalyst 33LV from Air Products GmbH, D-45527Hattingen) 2.0 parts by weight TCPP (trichloropropyl phosphate) 45.4parts by weight Desmodur ® T 80were thoroughly mixed and foamed to form a foam block. A very flexible,elastic, crack-free foam with a regular cell structure was obtained.

Example 10

100 parts by weight of the polyether from Example 2 3.0 parts by weightwater 0.8 parts by weight silicone stabiliser (OS ® 22, Th. GoldschmidtAG, D-45127 Essen) 0.1 parts by weight DMEA 0.05 parts by weight aminecatalyst (Niax ® A1, Witco Osi) 0.18 parts by weight tin octoate 40.5parts by weight Desmodur ® T 80were thoroughly mixed and foamed to form a foam block. A crack-free foamwas obtained.

Example 11 Cold-Cured Free Foam

Formulation:

50.0 parts by weight of the polyether from Example 1 50.0 parts byweight of a trifunctional polyether with an OH number of 28 mg KOH/gand > 80 mole % of primary OH groups (Desmophen ® VP PU 10WF22, BayerAG) 3.6 parts by weight water 0.15 parts by weight amine catalyst(Niax ® A1, Witco Osi) 0.4 parts by weight amine calalyst (catalyst 33LVfrom Air Products GmbH, D-45527 Hattingen) 1.25 parts by weightdiethanolamine 0.50 parts by weight silicone stabiliser (Tegostab ® B8708, Th. Goldschmidt AG, D-45127 Essen) 62.8 parts by weight highmonomer content 4,4′-diphenylmethane diisocyanate with polymer fractionsand an NCO content of 32.3 wt. % (VP PU Desmodur ® 3230, Bayer AG)

A high quality free foam was obtained.

Example 12 Hot-Cured Moulded Foam

Formulation:

100.0 parts by weight of the polyether from Example 2 3.5 parts byweight water 0.05 parts by weight tin octoate 0.15 parts by weight aminecatalyst (Niax ® A1, Witco Osi) 1.0 parts by weight silicone stabiliser(Tegostab ® B 4900, Th. Goldschmidt AG, D- 45127 Essen) 62.8 parts byweight Desmodur ® T 80

A high quality moulded foam was obtained. In order to determine the airpermeability of the foam, its flow resistance to an air stream wasmeasured with the apparatus illustrated in FIGS. 1-3.

The apparatus consists of a glass cylinder graduated in millimeters from0 to 350, whose internal diameter is 36 mm, and an inner tube of 7 mminternal diameter. This inner tube terminates at the top in a T-piece,to one side of which is connected an air supply and to the other side ofwhich is connected a hose with a measuring head. The hose for themeasuring head has an internal diameter of 12 mm and a length of 1.80 m.The glass cylinder is closed at the bottom and can be filled with watervia a funnel connected at the rear. The test equipment is connected viatwo stopcocks, a pressure-reducing valve and a hose of suitable lengthand suitable diameter to a compressed air source, the pressure-reducingvalve being adjusted to ca. 2.0 bar. The glass vessel is filled withdistilled water until the lower edge of the meniscus reaches theH₂O-hour mark. Stopcock 1 is then turned and the flow rate at stopcock 2is altered until the lower edge of the meniscus of the inner columnreaches the 0 mm mark, indicating that a preliminary pressure of 100 mmwater column has been set. After the setting of the preliminary pressurethe measuring head is placed without pressure on the sample and theheight of the water column in the inner tube is then read off. This isequal to the flow resistance of the sample.

The following values were determined: flow resistance of the foam core:100 mm water column; flow resistance of the foam plus skin: 300 mm watercolumn.

Example 13 Hot-Cured Moulded Foam

Formulation

100 parts by weight of the polyether from Example 1 3.5 parts by weightwater 0.15 parts by weight amine catalyst (Niax ® A1, Witco Osi) 0.10parts by weight tin octoate 0.50 parts by weight silicone stabiliser(Tegostab ® B 4900, Th. Goldschmidt AG, D- 45127 Essen) 40.6 parts byweight Desmodur ® T 80

A high quality moulded foam was obtained. The flow resistance of thesample was determined according to the procedure described in Example12. The following values were measured: flow resistance of the foamcore: 50 mm water column; flow resistance of the foam plus skin: 160 mmwater column.

Example 14 Hot-Cured Moulded Foam

30.0 parts by weight of the polyether from Example 1 70.0 parts byweight Desmophen ® 3426 L 3.5 parts by weight water 0.09 parts by weighttin octoate 1.00 parts by weight silicone stabiliser (Tegostab ® B 4900,Th. Goldschmidt AG, D- 45127 Essen) 40.6 parts by weight Desmodur ® T 80

A high quality moulded foam was obtained.

1. A flexible polyurethane foam which is the reaction product of (1) a polyisocyanate with (2) an isocyanate-reactive component comprising a polyether polyol produced by alkoxylation in the presence of a double metal cyanide catalyst having a terminal propylene oxide block, containing at least one ethylene oxide/propylene oxide mixed block and having a number average molecular weight of from 700 to 50,000 g/mole.
 2. The foam of claim 1 which is a hot cured molded foam.
 3. The foam of claim 1 which is a slabstock foam.
 4. The foam of claim 3 in which at least 50 mole % of the ethylene oxide/propylene oxide mixed block of the polyether polyol comprises polyoxypropylene units. 